Many research groups around the world are investigating approaches to accelerate the discovery and development of hydrogen storage materials and systems to meet Department of Energy (DOE) 2015 system-based targets. A hydrogen storage system includes all the components required to get hydrogen from a hydrogen storage material and provide it to the end device or operating system, e.g., a fuel cell. System components can include, e.g., storage tanks, heat exchangers, valves, tubing, pumps, and other components. However, weights must be considered before each individual component can be considered as a component within the selected operating system. System target goals have been developed through the FreedomCAR Partnership between DOE and the US Council for Automotive Research (USCAR, www.uscar.org). Ammonia borane (NH3BH3), denoted herein as (AB), has a potential to meet established targets for a viable hydrogen storage material and to provide hydrogen for use as an operating fuel. Several processes are described in the literature for synthesizing ammonia borane AB. In the conventional metathesis approaches, synthesis of AB involves two undesired pathways that involve formation of DADB, the ionic dimer of AB, as shown hereafter:2NH4BH4→2AB+2H2 2AB→DADB  (A)NH4BH4→AB+H2NH4BH4+AB→DADB+H2  (B)
In pathways (A) and (B), NH4BH4 decomposes to form AB with loss of H2 gas. However, as AB is formed, AB can dimerize as in pathway (A) to form DADB or can lose hydrogen and form polymeric polyaminoborane (PAB), a decomposition product. Alternatively, AB can also react with NH4BH4 as in pathway (B) to form DADB or PAB. Increasing the AB concentration or temperature increases the likelihood of reactions that form DADB and PAB. In these approaches, DADB is a competing reaction component that can decrease the yield of AB. In an alternative metathesis approach performed in an organic solvent, dilute reactant concentrations were used in an attempt to prevent DADB or PAB formation. However, low yields of AB were obtained. In another approach known in the art, an attempt was made to promote H2 loss from NH4BH4 in NH3 to form AB by heating (e.g., at 40° C.), but various and multiple reaction products were obtained by heating the NH3 solution that decreased the yield of AB as well as the purity of the product. In short, current methods are limited by problems including, e.g., dilute reactant concentrations; competing side reactions and products including, e.g., polymeric products (e.g., DADB and PAB); complex product recovery; toxic solvents; low product purity; and low product yields. Accordingly new methods are needed that improve reaction efficiencies and provide greater yields of AB at a greater purity.